Mixed-level factorial designs are experimental designs whose factors have different numbers of levels. These designs are very useful in experiments involving both qualitative and quantitative factors. One design approach is to run all possible combinations of the factor levels. However, as the number of factors or factor levels increases, the number of experiments increases dramatically. As a result, research has focused on developing orthogonal or near-orthogonal fractional factorial designs... Show moreMixed-level factorial designs are experimental designs whose factors have different numbers of levels. These designs are very useful in experiments involving both qualitative and quantitative factors. One design approach is to run all possible combinations of the factor levels. However, as the number of factors or factor levels increases, the number of experiments increases dramatically. As a result, research has focused on developing orthogonal or near-orthogonal fractional factorial designs. The property of design balance, that the same number of runs is performed for each factor level, has been maintained in currently proposed designs. In some cases, maintaining balance requires too many experimental runs. The objective of this thesis is to develop fractional mixed-level factorial designs with economical run size that have desirable properties associated with near-balance and near-orthogonality. Two criteria are developed to assess the degree of near-balance for comparing and constructing designs. A modified J2-optimality criterion is used for comparing design near-orthogonality. These criteria are combined to assess different design alternatives. A genetic algorithm is then used to build designs with the most desirable combination of near-balance and near-orthogonality. Show less

Carbon nanotubes are theoretically one of the strongest and stiffest materials with a calculated tensile strength of ~200 giga Pascal and modulus of more than 1-4 tera Pascal for a single walled nanotube (SWNT). If the mechanical properties of SWNT could be effectively incorporated into a polymer matrix, composites with lightweight, exceptional strength and stiffness can be achieved. The effective utilization of nanotubes in composites for applications depends on the ability to disperse the... Show moreCarbon nanotubes are theoretically one of the strongest and stiffest materials with a calculated tensile strength of ~200 giga Pascal and modulus of more than 1-4 tera Pascal for a single walled nanotube (SWNT). If the mechanical properties of SWNT could be effectively incorporated into a polymer matrix, composites with lightweight, exceptional strength and stiffness can be achieved. The effective utilization of nanotubes in composites for applications depends on the ability to disperse the nanotubes uniformly throughout the matrix. Carbon nanotubes are anisotropic in nature. Therefore to take advantage of the nanotubes in the axial direction, controlled tube orientation or degree of alignment of nanotubes in the polymer matrix is very important to realize their high mechanical and functional properties. The nanocomposites produced by current conventional methods using direct mixing, melt blending or solution casting have failed to yield significant improvements in composite modulus. Although tremendous progress has been made towards understanding the properties of individual carbon nanotubes, but attaining the true potential of the bulk polymeric nanocomposites have been hindered by the lack of uniform SWNT dispersion, poor interfacial bonding, inadequate tube loading and uncontrollable tube orientation or degree of alignment. This thesis work developed an innovative approach for producing nanocomposites that has uniform SWNT dispersion, high tube loading and most importantly controlled tube orientation. In this research, these properties in composites were achieved by using magnetically aligned buckypapers and resin infusion system. The aligned nanotube buckypaper and composite were characterized using AFM and SEM. The mechanical properties of these materials were experimentally determined using DMA and were theoretically verified. The electrical properties of these materials were also experimentally determined using 4-probe resistivity measurements. Significant tube alignment has been achieved in the resultant buckypaper and nanocomposites. It is shown that the developed method is an effective way for producing nanocomposites with uniform SWNT dispersion desired tube alignment and high tube loading. Show less

Date Issued

2003

Identifier

FSU_migr_etd-3403

Format

Thesis

Title

Development of Integrated Process Design Environment and Statistical Analysis of RTM Process.

The resin transfer molding (RTM) process has been used in the composite industry for decades. However, several issues still exist and impede its wide applications. Some design tools for RTM parts have been developed but a more efficient design environment is lacking. Race-tracking is a common phenomenon that makes prediction in actual production difficult and makes current deterministic optimal tooling design unrepeatable. This thesis integrates flow simulation and cost analysis modules... Show moreThe resin transfer molding (RTM) process has been used in the composite industry for decades. However, several issues still exist and impede its wide applications. Some design tools for RTM parts have been developed but a more efficient design environment is lacking. Race-tracking is a common phenomenon that makes prediction in actual production difficult and makes current deterministic optimal tooling design unrepeatable. This thesis integrates flow simulation and cost analysis modules together with database management system (DBMS) providing a prototype of the integrated design environment for RTM processes. Preform permeability, especially race-tracking permeability that significantly affects not only simulated but also experimental results, was the factor being investigated. This thesis introduces a statistical approach utilizing statistically distributed variables to explain the race-tracking permeability values. One-dimensional flow experiments were conducted to obtain the permeability values. Three types of distribution (gamma distribution, Weibull distribution and lognormal distribution) were chosen as candidates. Experimental data were fitted for the three distributions. A goodness-of-fit test was performed to find the one that best describes the experimental data. Taking into account the fact that the severe levels of race-tracking can be represented by statistically distributed variables, this thesis proposes an optimization approach to minimize the sensitivity of the mold design to uncertainty of race-tracking permeabilities by choosing the appropriate locations of gates and vents (robust tooling design). A sensitivity that indicates the process robustness was defined as objective and evaluated by RTMSim software both for 2D and 2.5D geometry. With the conclusion that the ratios of race-tracking permeability over average values can be described by Weibull distributed variables, a random number generator was employed to generate the input race-tracking permeability data for obtaining values of the objective. Locations of vents were determined via the assumption that vents should be assigned at the locations where flow ends to avoid dry spot formation. Locations of gate were optimized from most possible locations. Show less

Most of the Federal Motor Vehicle Safety Standards applicable to school buses do not specifically cover the cutaway type of buses assembled on ladder-type chassis, for which a production process is split into two stages. In the first stage, the chassis and cab section are assembled by automobile manufacturers. In the second stage, the vehicle is shipped to another company where the bus body and additional equipment are installed. Lack of strict structural standards for transit bus body... Show moreMost of the Federal Motor Vehicle Safety Standards applicable to school buses do not specifically cover the cutaway type of buses assembled on ladder-type chassis, for which a production process is split into two stages. In the first stage, the chassis and cab section are assembled by automobile manufacturers. In the second stage, the vehicle is shipped to another company where the bus body and additional equipment are installed. Lack of strict structural standards for transit bus body builders necessitates the crashworthiness and safety evaluation of this category of vehicles. Such an assessment process is imperative since these transit buses are often used to transport disabled passengers. A full scale crash test is considered the most reliable source of information regarding structural integrity and safety of motor vehicles. However, the high cost of such tests and difficulties in collecting data results in an increasing interest in the analytical and computational methods of evaluation. Theses methods allow for extensive safety studies once the finite element model is validated. A reliable analytical investigation can reduce the cost dramatically and allow faster introduction of the new solutions. This thesis research work presents the procedure for development of a finite element (FE) model of a public transit bus and the results of its crashworthiness and structural integrity analysis. The finite element model was developed based on the geometry obtained by disassembling and digitizing all major parts of the actual bus. The FE model consists of 73,600 finite elements, has 174 defined property sets (groups of elements with the same features) and 23 material models. All parts are connected using different multi point constraints and special links with failure to model actual types of structural connections such as bolts and spot welds. LS-DYNA non-linear, explicit, 3-D, dynamic FE computer code was used to simulate behavior of the transit bus under different impact scenarios, such as frontal impact and side impact at various velocities. Show less

Date Issued

2003

Identifier

FSU_migr_etd-2589

Format

Thesis

Title

Investigation and Development of the Resin Infusion Between Double Flexible Tooling (RIDFT) Process for Composite Fabrication.

This research presents a study on an innovative composite manufacturing process called Resin Infusion between Double Flexible Tooling (RIDFT). In this process, resin is infused between two flexible tools through fiber reinforcements in a two-dimensional flat shape. The wetted reinforcements and flexible tooling are then formed over a mold into a specified part shape by use of vacuum. The RIDFT process has potentials for rapidly and affordably producing large composite parts. This research... Show moreThis research presents a study on an innovative composite manufacturing process called Resin Infusion between Double Flexible Tooling (RIDFT). In this process, resin is infused between two flexible tools through fiber reinforcements in a two-dimensional flat shape. The wetted reinforcements and flexible tooling are then formed over a mold into a specified part shape by use of vacuum. The RIDFT process has potentials for rapidly and affordably producing large composite parts. This research details the development of the industrial RIDFT machine from its design to its fabrication and to the demonstration of its use. This new machine uses new techniques, integrating vacuum sealing, dynamic supporting and temporary resin distribution channels to achieve industrial application requirements. A design of experiment (DOE) approach is used to perform testing and analysis to validate the ability of the RIDFT process to form various geometries and identify limitations in formability and issues with wrinkling. Four specific fiber textile structures were studied in their ability to form over a half sphere of varying radii and a rectangular mold of varying corner radii. The number of fiber layers was also studied to understand the effects on forming. Fiber textile structure and fiber layers were shown to be significant for their influence on formability and wrinkling. To better understand the forming mechanics within the RIDFT process and to predict the formability of a desired geometry, a simulation model was required. The PAMFORM software was chosen for modeling because it is a general-purpose finite element package for the industrial virtual manufacturing of non-metallic sheet forming. PAMFORM is unique in its ability to model a variety of forming processes. This research details the development of the simulation model for the RIDFT process based on PAMFORM and describes the validation of the model through experimental methods. This development includes the modeling of multiple layers of resin-wetted reinforcements, silicone diaphragms and part geometries, as well as the modeling of contact interfaces and forming pressures. The systematic investigation has been done for characterizing fabric drapability, rubber deformation and friction interactions for developing the simulation model. The model results are then compared against experimental results for model validation. This validated model will allow the ability to predict drapability and fiber deformation during the process forming. The results of the simulation reveal mechanisms and influence factors of the drapability and wrinkling of the RIDFT process. Show less

The removal of particles, on the order of a micrometer – nanometer in size, adhered to surfaces poses a challenge to Integrated Circuit (IC) fabrication, space optics, high resolution and high power optics, large area displays, magnetic storage device and other critical surfaces. The existing cleaning processes are unable to clean particulate contamination at the sub-micron level. Laser Particle Removal (LPR) is a novel technique to remove micron and submicron particulate contamination from... Show moreThe removal of particles, on the order of a micrometer – nanometer in size, adhered to surfaces poses a challenge to Integrated Circuit (IC) fabrication, space optics, high resolution and high power optics, large area displays, magnetic storage device and other critical surfaces. The existing cleaning processes are unable to clean particulate contamination at the sub-micron level. Laser Particle Removal (LPR) is a novel technique to remove micron and submicron particulate contamination from the solid surface. In LPR, a vapor of an Energy Transfer Medium (ETM) is condensed on the Si substrate. The vapor forms a uniform film on and around the particles. After a short time lag a KrF laser beam is used to irradiate the Si substrate which causes explosive evaporation of the ETM and propels the particle off the substrate. The ETM film thickness should be a critical factor in the LPR process. In our experiments a KrF laser at 248 nm is used to remove polystyrene particles of 0.1 ìm, 0.25 ìm and 0.55 ìm in radius from a Si substrate using 2-propanol as the ETM. The Cleaning threshold fluence for these particles at varying ETM film thicknesses is measured. In the end of this work the molecular dynamics simulations of laser cleaning process is discussed. Show less

Date Issued

2003

Identifier

FSU_migr_etd-1742

Format

Thesis

Title

Development of Framework for Rapid Tool Manufacture for RIDFT Process.

Polymer composites are in a period of significant growth due to the increased use in the automobile, marine and aerospace application. Some of the advantages of using composites over other materials are weight savings, corrosion resistance and functional integration. However, long cycle times and higher tooling costs of the available manufacturing processes make it difficult to mass-produce composite products. Resin infusion double flexible tooling (RIDFT) is a novel process developed by the... Show morePolymer composites are in a period of significant growth due to the increased use in the automobile, marine and aerospace application. Some of the advantages of using composites over other materials are weight savings, corrosion resistance and functional integration. However, long cycle times and higher tooling costs of the available manufacturing processes make it difficult to mass-produce composite products. Resin infusion double flexible tooling (RIDFT) is a novel process developed by the Florida Advanced Center for Composite Technologies (FAC2T) at FAMU-FSU College of Engineering aimed at tackling some of the above-mentioned problems. The use of one-sided mold provides a huge cost advantage over Resin Transfer Molding (RTM). However, using cost effective materials can reduce the cost further. In this thesis research, the various steps involved in the manufacture of the RIDFT mold were identified. The seven steps to manufacture a RIDFT mold are, Initial Graphics Exchange Standard (IGES) file tooling import/repair, mold design, material selection and preparation, NC programming, machine setup, machining and finishing and polishing. The problems at each of these stages were identified. The solutions to some of the problems, which might result in decrease in the tool manufacturing time, were found. To tackle with IGES file import problems some guidelines are presented. The various steps involved in the mold design stage are: compensation of permeable layer thickness, compensation of silicone layer thickness compensation of thickness of part and addition of draft surface. The tooling parameters compensation part of the mold design process was implemented by using both offset and scaling methods using C programming. The materials used for tooling until now are reviewed for pros and cons. Some of the tooling materials, that can be used in future, are also suggested. In order to help the mold manufacturer with the selection of machining parameters a macro was written in Microsoft Excel. Three cases were studied to show how the objectives of thesis are met. Show less

A 81-mm mortar barrel that is at least 50% lighter than the current steel barrel used in the M252 mortar system would prove to be advantageous for the army. The desire for the weight reduction was based on the army's vision of the future combat systems. The current barrel has a maximum rated pressure of 109 MPa (15,800 psi) and is capable of sustained fire rates of 15 rounds per minute. The concept of sheathing a steel liner with a lightweight material to meet the weight saving goal while... Show moreA 81-mm mortar barrel that is at least 50% lighter than the current steel barrel used in the M252 mortar system would prove to be advantageous for the army. The desire for the weight reduction was based on the army's vision of the future combat systems. The current barrel has a maximum rated pressure of 109 MPa (15,800 psi) and is capable of sustained fire rates of 15 rounds per minute. The concept of sheathing a steel liner with a lightweight material to meet the weight saving goal while satisfying the performance requirements was investigated. The perceived need for lightweight mortars led to the study of composite materials. Composites are increasingly being used because of their lightweight, high strength to stiffness ratio and high durability under severe loading environments. High temperatures around 550oC (1022oF) are produced in the mortar barrel during firing. Very few resins are now available that are susceptible to working temperatures of as high as 350oC (662oF). A thermal barrier material was introduced between the steel liner and the composite sheath to reduce the transmission of high temperatures to the sheath, hence reducing the working temperature of the resin. Viable materials for the barrel were investigated and identified. 4340 steel was considered for the liner material, Nextel 610/Sialyte composite for the thermal barrier material and IM7/cyanate ester composite for the sheath material. The lightweight composite mortar barrel was modeled and analyzed using the finite element analysis software ABAQUS. Finite element analysis was conducted on the mortar barrel to determine the integrity of the design against the maximum expected pressure and temperature loads. The failure strength analysis determined that the design was susceptible to the rated loads. The weight of the composite mortar barrel was evaluated to be 5.3 Kg (11.68 lb) while the weight of the current steel barrel is 12.4 Kg (27.4 lb). The composite mortar barrel design achieved a potential weight reduction of 57% compared to that of the current steel barrel. Show less

This dissertation presents a systematic study on the dimension variation prediction and control for polymer matrix fiber reinforced composites. A dimension variation model was developed for process simulation based on thermal stress analysis and finite element analysis (FEA). This model was validated against the experimental data, the analytical solutions and the data from literature. Using the FEA-based dimension variation model, the deformations of typical composite structures were studied... Show moreThis dissertation presents a systematic study on the dimension variation prediction and control for polymer matrix fiber reinforced composites. A dimension variation model was developed for process simulation based on thermal stress analysis and finite element analysis (FEA). This model was validated against the experimental data, the analytical solutions and the data from literature. Using the FEA-based dimension variation model, the deformations of typical composite structures were studied and the regression-based dimension variation model was developed. The regression-based dimension variation model can significantly reduce computation time and provide a quick design guide for composite products with reduced dimension variations. By introducing the material modification coefficient, this comprehensive model can handle various fiber/resin types and stacking sequences. It eliminates the complicated, time-consuming finite element meshing and material parameter defining process. The deformation compensation through tooling design was investigated using the FEA-based and the regression-based dimension variation models. The structural tree method (STM) was developed to compute the assembly deformation from the deformations of individual components, as well as the deformation of general shape composite components. The STM enables rapid dimension variation analysis/synthesis for complex composite assemblies with the regression-based dimension variation model. Using the STM and the regression-based dimension variation model, design optimization and tolerance analysis/synthesis were conducted. The exploring work presented in this research provides a foundation to develop practical and proactive dimension control techniques for composite products. Show less

Supply chain optimization is a set of approaches utilized to efficiently integrate suppliers, manufacturers, warehouses, and stores, so that merchandise is produced and distributed at the right quantities, to the right locations, and at the right time, in order to minimize system-wide costs, while satisfying service level requirements. The proposed study addresses the issue of supply chain optimization amongst three companies: Vistakon, which sources the cartons to package ACUVUE contact lens... Show moreSupply chain optimization is a set of approaches utilized to efficiently integrate suppliers, manufacturers, warehouses, and stores, so that merchandise is produced and distributed at the right quantities, to the right locations, and at the right time, in order to minimize system-wide costs, while satisfying service level requirements. The proposed study addresses the issue of supply chain optimization amongst three companies: Vistakon, which sources the cartons to package ACUVUE contact lens; North State Cartons, which is the carton supplier; and Durango Paper Company, which is the paperboard supplier. An effort is made to integrate the production and information flow and ensure timely production and distribution of the cartons, which reduced the lead-times and inventory levels at Vistakon's, North State Carton's, and Durango Paper Company's site location. The complete supply chain solution to optimize the existing system is provided and the ordering process solution is presented in the form of service level models. As a result of optimized supply chain management, the overall lead-time of the complete cartons manufacturing and procurement process is enormously reduced. The supply chain member organizations are benefited by reduced carton inventory levels, effective demand forecasting system, better inventory management system, improved information sharing system, decreased annual setup cost, and increased annual savings. Show less

Carbon nanotubes have exceptional mechanical and functional properties and are considered by many as the most promising reinforcement for the next generation high performance nanostructured materials. Tubes dispersion and interfacial bonding are the most critical issues for developing carbon nanotube-reinforced composites. Considerable improvements in the dispersion and interfacial bonding of single-walled carbon nanotube (SWNT)/ epoxy nanocomposites were obtained through developing new... Show moreCarbon nanotubes have exceptional mechanical and functional properties and are considered by many as the most promising reinforcement for the next generation high performance nanostructured materials. Tubes dispersion and interfacial bonding are the most critical issues for developing carbon nanotube-reinforced composites. Considerable improvements in the dispersion and interfacial bonding of single-walled carbon nanotube (SWNT)/ epoxy nanocomposites were obtained through developing new fabricating techniques and functionalized SWNTs in this thesis research. By systematically investigating dispersion formulations, processing parameters, mechanical property tests and SEM observations, better tubes dispersion were achieved while dispersing nanotubes in a special dispersion system to form a stable solution and then mixing it with epoxy resin. Further functionalized nanotubes also improve the dispersion. Functionalization methods such as chopping, chopping-oxidizing, molecular wraping and directly oxidizing were used to create more active sites in the nanotubes for enhancing tube-resin interaction during processing and composite interface. Interfacial bonding improvement was studied through mechanical tests and SEM observations. The results shows that the storage modulus of nanocomposites is improved over the neat epoxy resin through better tubes dispersion, functionalized nanotubes as well as higher tubes loading. However, the addition of nanotubes resulted in the glass transition degradation of the resulting nanocomposites. This thesis research developed new methods of dispersion and fabrication of nanotube composites, which considerably enhances tube dispersion and mechanical properties of the resultant nanocomposites. The results also reveal that modified tubes using the selected functionalization methods can be used to improve both tube dispersion and interface bonding in the nanocomposites. Show less

Date Issued

2003

Identifier

FSU_migr_etd-1383

Format

Thesis

Title

Thermal Conductivity and Coefficients of Thermal Expansion of SWNTs/Epoxy Nanocomposites.

Since their discovery in 1991, carbon nanotubes have undergone intensive research. The single-walled carbon nanotube, or SWNT, has a unique electronic structure. According to their chirality, they can be either metallic or semiconductors with various band gaps. These different electronic structures influence their electrical and thermal properties. Studies have been conducted to understand, model and measure their electrical and thermal properties by computer simulation and experimental... Show moreSince their discovery in 1991, carbon nanotubes have undergone intensive research. The single-walled carbon nanotube, or SWNT, has a unique electronic structure. According to their chirality, they can be either metallic or semiconductors with various band gaps. These different electronic structures influence their electrical and thermal properties. Studies have been conducted to understand, model and measure their electrical and thermal properties by computer simulation and experimental measurements. Even though current research shows inconsistent results, all studies show that SWNTs have phenomenal electrical and thermal properties. To take advantage of these unique properties of nanotubes requires properly incorporating SWNTs into a matrix as a reinforcement or filler to form nanocomposites with desired properties. Carbon nanotube reinforced composites are still under development. The mechanical properties of these materials have been intensively explored; however, the electrical and thermal properties still require further study. The main objective of this thesis was to measure and understand the thermal behavior of SWNT-reinforced composites. This thesis focuses on 1) the thermal conductivity of buckypapers (aligned or random SWNT network from filtration of well-dispersed nanotube suspension) and the nanocomposites produced from the buckypapers, and 2) the influence of nanotubes on thermal expansion by direct mixing and casting samples of SWNT/epoxy nanocomposites. Thermal conductivity was measured using a comparative method, with a constantan foil as a reference. The temperature dependence of the thermal conductivity was measured from 115 K to room temperature. Magnetically aligned buckypapers produced with 17.3 Tesla magnetic field showed the highest thermal conductivity at room temperature, with a maximum value of 41.5 W/mK in the aligned direction. The coefficient of thermal expansion (CTE) was measured using the Thermomechanical Analyzer (TMA). The influence of nanotube functionalization and loading on the CTE of the epoxies revealed that adding 1 wt% nanotubes in the epoxy resin could reduce the CTE of the resin as much as 35.5%. The mechanisms of thermal conductivity variation and CTE reduction in the buckypapers and nanocomposites are also discussed. Show less

Date Issued

2004

Identifier

FSU_migr_etd-4142

Format

Thesis

Title

Computerization and Automation of Affordable Traffic Data Collection System for the State of Florida.

The Florida Department of Transportation has initiated and funded development of electronic crash and citation reporting in Florida using the TraCS (Traffic and Criminal Software) platform. The TraCS system is application software that is a customizable data collection system that can be used by law enforcement and motor vehicle agencies to collect crash data. TraCS is combined with laptop computers, one or more personal computers (PC) in a central office. Peripherals such as image/bar code... Show moreThe Florida Department of Transportation has initiated and funded development of electronic crash and citation reporting in Florida using the TraCS (Traffic and Criminal Software) platform. The TraCS system is application software that is a customizable data collection system that can be used by law enforcement and motor vehicle agencies to collect crash data. TraCS is combined with laptop computers, one or more personal computers (PC) in a central office. Peripherals such as image/bar code scanners and mobile printers, and data communications are in conjunction with TraCS to provide officers with all of the functionality needed to record and retrieve incident information wherever and whenever an incident occurs. The thesis objectives were to perform time study analysis and to investigate costs of current and proposed (TraCS-based) methods. The TraCS software was developed, and in the summer of 2003; seven Florida law enforcement agencies were selected to pilot and test electronic crash and citation reporting. The agencies were provided with required equipment and training to use TraCS software. The ride-alongs were performed with Jacksonville Sheriff's Office and Leon County Sheriff's Office (two of the pilot agencies). During the ride-alongs, the time taken to complete forms both with and without TraCS software was measured and the data analysis was performed. The study shows that the efficiency and accuracy of Florida traffic records was improved by using the electronic data collection system (TraCS). Data analysis showed that it takes less time to fill a crash report using TraCS compared to filling out a crash report manually on a paper form. On an average for the two vehicle crashes the time saved by using TraCS software to fill long form, short form, and driver exchange form were 11.7%, 11.3% and 8.3%, respectively. The time to fill a citation form using TraCS software was reduced by 13.6% from the time without TraCS. The software had best application when used in conjunction with the magnetic stripe reader for Florida driver license. The efficiency of officer's using TraCS differs based on the learning curve, equipment provided, and mindset of an officer. After suitable training the time taken to complete a report should decrease even further. Show less

Industrial manufacturing processes can experience a variety of changes to important quality characteristics as a result of tool breakage, tool wear, introduction of new raw materials, and other factors. Statistical process control charts are often used to monitor for changes in quality characteristics for manufacturing processes. The control chart computes a statistic based on measured observations of the process and compares it to control limits. When the statistic exceeds a control limit,... Show moreIndustrial manufacturing processes can experience a variety of changes to important quality characteristics as a result of tool breakage, tool wear, introduction of new raw materials, and other factors. Statistical process control charts are often used to monitor for changes in quality characteristics for manufacturing processes. The control chart computes a statistic based on measured observations of the process and compares it to control limits. When the statistic exceeds a control limit, the control chart signals that the process is out-of-control. Quality engineers would then search for the special cause responsible for the change in the process. Rapid detection by the control chart is important to minimize the production of poor quality items as a result of an out-of-control process. Control charts that detect changes rapidly can therefore save critical process down-time and expense. This research investigates several new control charts related to the commonly used cumulative sum (CUSUM) control chart. The new control charts use control limits that change as a function of the number of process observations instead of remaining constant. The performances of these new control charts are compared to several other charts including the Shewhart chart, the CUSUM, and the exponentially weighted moving average charts. Compared to the standard CUSUM, the proposed control charts can detect a change in a process more rapidly for a given range of shifts in the mean of a process. The proposed control charts offer a flexibility to quality engineers for better optimization of monitoring schemes for manufacturing processes. Show less

Date Issued

2004

Identifier

FSU_migr_etd-2593

Format

Thesis

Title

Investigation of Vartm Processing of High Temperature RP-46 Resin System.

The advantages of using polymer matrix composites in various applications are very well known throughout many industries. Their introduction and subsequent development since the 1940's has led to major cost savings due to their lightweight and excellent mechanical properties. Off late, product designers have been taking advantage of improved thermal properties (CTE, thermo-oxidative stability) that these composite materials have to offer. This began with the development of PMR-15, a high... Show moreThe advantages of using polymer matrix composites in various applications are very well known throughout many industries. Their introduction and subsequent development since the 1940's has led to major cost savings due to their lightweight and excellent mechanical properties. Off late, product designers have been taking advantage of improved thermal properties (CTE, thermo-oxidative stability) that these composite materials have to offer. This began with the development of PMR-15, a high temperature polyimide resin back in the 1970's. The aerospace industry has increasingly turned towards high temperature polymer matrix composites (HTPMC) to replace other heavier materials in engine components thus improving the thrust to weight of the engine. But, PMR-15 has a major drawback related to high safety standards that are needed during processing. The implementation of these controls during processing resulted in huge costs to the industry. This led to the development of a new polyimide high temperature resin system called RP-46 at NASA Langley research center. RP-46 has excellent thermal and mechanical properties comparable to PMR-15 and is safer to handle due to the absence of the lethal MDA monomer, a carcinogen. This research investigates the issues related to processing of RP-46 resin system using the Vacuum Assisted Resin Transfer Molding (VARTM) process, a cost effective method for manufacturing composite materials. The entire process is setup keeping in consideration the requirement of high temperature environments for processing of RP-46. A number of initial trials helped understand the dynamics of the process and identify critical factors and key parameters. The various laminates that were made were tested for mechanical properties (ASTM D3039 - Tensile strength and modulus) and thermal properties (Dynamic Mechanical Analysis, Thermal Mechanical Analysis, Thermal Gravimetric Analysis) were performed and the results were compared with RP-46 samples made using autoclave processing. Although the VARTM laminates had issues related to void contents and the release of volatiles during the infusion stage of the process, the VARTM process was found to be feasible to make composites with RP-46. Show less

The discovery of single-walled nanotubes (SWNTs) gives an important boost to nanomaterial research. Since the nanotubes have exceptional mechanical, thermal, and electrical properties, they are considered very promising reinforcement materials for developing high performance nanocomposites. One of the effective methods for fabricating nanotube composites is to make nanotubes into buckypaper form (Nanotube Buckypaper). The nanotubes are pre-formed into buckypaper of well-dispersed tube network... Show moreThe discovery of single-walled nanotubes (SWNTs) gives an important boost to nanomaterial research. Since the nanotubes have exceptional mechanical, thermal, and electrical properties, they are considered very promising reinforcement materials for developing high performance nanocomposites. One of the effective methods for fabricating nanotube composites is to make nanotubes into buckypaper form (Nanotube Buckypaper). The nanotubes are pre-formed into buckypaper of well-dispersed tube network, so as to control tube dispersion and loading as well as microstructures in the resulting composites. In this research, we characterized the quality of buckypaper with different fabricating parameter combinations, and performed statistical analysis on the quality of the produced buckypapers. A statistical model of the nanotube buckypaper process was developed to investigate the contribution of fabricating parameters, including suspension concentration, sonication level and time, filtration vacuum pressure, and surfactant types on nanotube bundle quality as measured by rope size and pore size. Statistical modeling is also used to estimate the variability associated with manufacturing, the image taken, and the measurement processes. The statistical analysis shows that all the selected factors are influential to the quality of buckypaper, and the interactions between these factors contribute more than the factors themselves. Overall, the selection of surfactant is crucial to the formation of a uniform tube rope network of nanotube buckypaper in both average performance and variability. The microscopy characterization of the nanotube buckypaper samples, designed experiment, and variance components analysis all provide strong evidence that Triton X-100 is the best surfactant in terms of better dispersion effect, higher repeatability and less variability in producing nanotube buckypapers. Therefore, the process of fabricating buckypaper with Triton X-100 is suggested to construct a reliable and repeatable model of nanotube buckypaper process, and the model can be further used to optimize operating parameters and predict the quality of nanotube buckypapers. Show less

Date Issued

2004

Identifier

FSU_migr_etd-0420

Format

Thesis

Title

In-Mold Coating of Composites Manufactured with the Resin Infusion Between Double Flexible Tooling Process by Means of Co-Infusion.

As composite materials gain wider acceptance within the transportation industry, it is pertinent to investigate the available coating processes with a view to reduce emissions and associated costs. Current painting processes are not only laborious and time consuming, but expensive and present safety issues. In-mold coating presents an avenue for eliminating on reducing theses problems. This work aims to determine the feasibility and develop a methodology for In-Mold Coating (IMC) components... Show moreAs composite materials gain wider acceptance within the transportation industry, it is pertinent to investigate the available coating processes with a view to reduce emissions and associated costs. Current painting processes are not only laborious and time consuming, but expensive and present safety issues. In-mold coating presents an avenue for eliminating on reducing theses problems. This work aims to determine the feasibility and develop a methodology for In-Mold Coating (IMC) components manufactured using the Resin Infusion between Double Flexible Tooling (RIDFT) process. Comparisons of the cost and efficiency between a component manufactured by RIDFT and then painted, and a component manufactured by RIDFT IMC process is given. It indicates a 46% savings in capital investment and 55% savings in time while using RIDFT IMC. The viability of in-mold coating RIDFTed components was investigated. This work-in-process, reports on successes and challenges presented, during the co-infusion of a polyurethane enamel paint (DuPont Imron 5000) and a vinyl ester resin (Derakane 470-45). In this thesis, RIDFT IMC is used to manufacture a double-layered structure consisting of a vinyl ester layer for structural function and a polyurethane enamel coating layer. The two liquids are either simultaneously or sequentially infused into a double flexible mold and are cured. Liquid separation is maintained by a separation layer. Twenty-four case studies have been made to determine the viability of the IMC process. Eight different separation layers were tested to find out the most promising separating material. The specification of the separation layer was made. Several test evaluations were conducted. A Differential Scanning Calorimeter (DSC) is used to test the cure cycle for the resin and the paint. Mechanical testing, Dynamic mechanical analysis (DMA) and tensile tests are used to evaluate the performance of the produced parts. An Environmental Scanning Electron Microscope (ESEM) was used to evaluate the microstructure of the components. In order to improve the flow of the fluids, several Flow Distribution Channels (FDCs) were made and tested to determine the best configuration. The experimental results demonstrate that in-mold coating by means of co-infusion may be a viable option for painting RIDFT components with determination of an appropriate separation layer. The paint used in this work dissolves the separation layer. Further work has been suggested to develop a paint formulation that will not dissolve the separation layer. Show less

Date Issued

2004

Identifier

FSU_migr_etd-3804

Format

Thesis

Title

Development of the RIDFT Process Incorporation of Ultraviolet Curing Technique.

Polymer composite manufacturing techniques have over the years generated tremendous interest in the area of research and development in response to current trends and demands. Recent studies have focused on the development of several variations of liquid composite molding (LCM) techniques for the manufacture of polymeric composite parts. These techniques, which include processes such as Resin Transfer Molding (RTM), Vacuum Assisted Resin Transfer Molding (VARTM), Seemann Composite Resin... Show morePolymer composite manufacturing techniques have over the years generated tremendous interest in the area of research and development in response to current trends and demands. Recent studies have focused on the development of several variations of liquid composite molding (LCM) techniques for the manufacture of polymeric composite parts. These techniques, which include processes such as Resin Transfer Molding (RTM), Vacuum Assisted Resin Transfer Molding (VARTM), Seemann Composite Resin Infusion Molding Press (SCRIMP), have gained wide spread acceptance within the composite industry, primarily because they attempt to eliminate or reduce most, of the styrene emissions associated with open mold composite manufacturing techniques. Nonetheless, LCM techniques have found limited use in the mass production sector due to long production cycle times This work is centered on the process development of the Resin Infusion between Double Flexible Tooling (RIDFT). Despite the tremendous potential benefits that can be obtained from the RIDFT process, it is still plagued by some of the inherent limitations generally prevalent amongst most closed mold technology LCM processes. These limitations arise primarily because RIDFT, just like other LCM processes, makes use of an organic peroxide based catalyst curing system that invariably introduces a certain amount of inflexibility and restriction in the overall manufacturing process. These include long production cycle times due to lengthy curing times, as well as a narrow processing window for the production of composite parts. The primary focus of this thesis is to evaluate the feasibility of designing and incorporating a Cure on Demand (C.o.D) system into the RIDFT process that would involve the use of Ultraviolet (UV) light for the curing of composite laminates. The objective is to develop a process for the RIDFT that would eliminate or reduce the inflexibility in the current production process, resulting in shortened production cycle times. UV cured laminates were produced at a fraction of the time required to produce catalyst cured laminates. Mechanical and material characterization tests were performed on each of the UV cured laminates produced. The results were referenced against that obtained for laminates produced using a catalyst curing system to determine their overall quality. The UV cured laminates after undergoing both tensile and rheological thermal tests were found to have both mechanical and material properties that were comparable and in a few instances slightly better than that of thermally cured laminates. Show less

Poisson count process are often used to model the number of occurrences over some interval unit. In an industrial quality control setting, these processes are often used to model the number of nonconformities per unit of product. Current methods used for monitoring and estimating changes in Poisson count processes assume that the magnitude and type of change are known a priori. Since rarely in practice are these known, this dissertation reports on the development and evaluation of several... Show morePoisson count process are often used to model the number of occurrences over some interval unit. In an industrial quality control setting, these processes are often used to model the number of nonconformities per unit of product. Current methods used for monitoring and estimating changes in Poisson count processes assume that the magnitude and type of change are known a priori. Since rarely in practice are these known, this dissertation reports on the development and evaluation of several methods for detecting and estimating change points when the magnitude and type of change are unknown. Instead, the only assumption requires that the type of change belongs to a family of monotonic change types. Results indicate that the methodologies proposed throughout this dissertation research provide robust detection and estimation capabilities (relative to current methods) with regard to the magnitude and type of monotonic change that may be present. Show less

High performance composites are currently being used in the marine, automotive, aerospace and defense industries. These industries demand materials with properties that are similar or better than conventional metals at a fraction of the weight. The development of nanoparticle reinforced composites is presently one of the most explored areas in materials science and engineering. The exceptional properties of nanoparticles have made them a focus of widespread research. By combining... Show moreHigh performance composites are currently being used in the marine, automotive, aerospace and defense industries. These industries demand materials with properties that are similar or better than conventional metals at a fraction of the weight. The development of nanoparticle reinforced composites is presently one of the most explored areas in materials science and engineering. The exceptional properties of nanoparticles have made them a focus of widespread research. By combining nanoparticles with traditional reinforcement materials, multiscale composites can be produced with superior properties to that of regular composites. This research focuses on the development of multiscale reinforcement composites, through the use of carbon nanotubes (CNTs), IM7 and T800 carbon fibers and SC-79 epoxy resin. Vacuum assisted resin transfer molding and hand lay-up/ vacuum bagging processes were evaluated for the manufacturing of multiscale composites. Results from this research showed that the use of carbon nanotubes can increase the tensile strength by up to 27% and toughness by up to 38%, with the addition of 2.5wt% multiwall carbon nanotubes (MWNTs). However there were no significant changes in the flexural properties with the addition of carbon nanotubes. Analysis of the fracture surfaces, using scanning electron microscopy showed that there was good dispersion of the carbon nanotubes through out the matrix material. The good dispersion of tubes aided in toughening the SC-79 epoxy resin. This toughening effect was evident though the change in crack propagation patterns on the fracture surface. There was also evidence of the nanotubes bridging cracks and holding resin particles together, which also lead to increased fracture toughness Show less

Date Issued

2005

Identifier

FSU_migr_etd-0823

Format

Thesis

Title

Model Characteristics and Properties of Nanorobots in the Bloodstream.

Many researchers have various visions and concepts about what the nanorobot will be like and what they will do. Most people see nanorobots doing a lot of functions in the medical field, having ideas of them doing cell repair, seek-and-destroy harmful diseases, clean arteries of cholesterol buildup, and much more. There are many questions that need to be answered as to what exactly is needed for the nanorobot to perform these medical functions. This project is not interested in the design of... Show moreMany researchers have various visions and concepts about what the nanorobot will be like and what they will do. Most people see nanorobots doing a lot of functions in the medical field, having ideas of them doing cell repair, seek-and-destroy harmful diseases, clean arteries of cholesterol buildup, and much more. There are many questions that need to be answered as to what exactly is needed for the nanorobot to perform these medical functions. This project is not interested in the design of the nanorobot, but focuses on the characteristics and parameters that should be considered for a nanorobot to function through the bloodstream of a human body, specifically. To do this, a mobile robot was being used to traverse through a scaled model of the bloodstream. The scale model consisted of clear tubing or piping enclosed in a loop filled with liquid to nearly the exact viscosity of blood. The liquid had particles to emulate the various obstacles that a nanorobot would encounter like red blood cells and other molecules. The simulation had a continuous flow at the appropriate rate and pressure expected in the bloodstream. The pipe size was calculated setting the ratio of the diameter of a particular blood vessel over the diameter face of the assumed size of a nanorobot (DBV / DNR) equaling the diameter of the pipe (unknown variable) to the diameter face of the mobile robot (DPipe / Dsub). The pipe size came to be 6.66 inches, however pipe sizes come in increments of 2 inches larger than 4 inch pipes. It was settled to use 6 inch pipes. With this variable, the Reynolds number is the diameter of pipe times the velocity of the fluid over the kinematic viscosity of the fluid (R = (DPipe * ν) / υ). Setting the Reynolds value of the bloodstream equal to the Reynolds value of the model, the velocity of the pipe could be isolated. With that the flow rate was evaluated by multiplying the velocity to the cross-sectional area of the pipe (Flow Rate was equal to 0.2021392 gallon/minute). With all conditions met for an accurate model of the bloodstream, the physical model was designed and constructed then testing with the mobile robot was done to determine how the robot functions in the simulated environment. The results of the experiment showed that the mobile robot is influenced by the environment. The speed it travels decreases as viscosity of the fluid increases. The particles in the fluid also affect the speed along with the flow of the fluid. Mobility and control of the mobile robot were hindered with the increase of viscosity and the presence of particles. When traveling against the flow of the fluid it was further hindered. Stability of the craft increased along with viscosity but was chaotic traveling with particles. The performance of the mobile robot was affected by the conditions and parameters involved in the bloodstream. Show less

Date Issued

2005

Identifier

FSU_migr_etd-0496

Format

Thesis

Title

Characterization and Analysis of Electrical Conductivity Properties of Nanotube Composites.

Carbon nanotubes have attracted tremendous attention in both industrial and academic world due to their incomparable attributes in various areas since their first discovery. In recent years, as one of the most distinctive applications, conductive carbon nanotube composites have been investigated. Comparing with traditional materials, conductive nanocomposites have several advantages including extra-low threshold of particle content, no degradation of mechanical properties, ability to absorb... Show moreCarbon nanotubes have attracted tremendous attention in both industrial and academic world due to their incomparable attributes in various areas since their first discovery. In recent years, as one of the most distinctive applications, conductive carbon nanotube composites have been investigated. Comparing with traditional materials, conductive nanocomposites have several advantages including extra-low threshold of particle content, no degradation of mechanical properties, ability to absorb magnetic interference, and tunable conductivity. The main objectives of this thesis were to develop a comprehensive electrical resistivity measurement system which can cover resistivity range from 10E-6 to 10E18 §Ùcm and understand the relationship between their nanostructure and electrical resistivity. The resistivity of various nano-materials produced at FACCT including random and aligned buckypaper (BP), direct mixing and casting samples, BP composites, and multi-scale composites were investigated and characterized. It was found that less than 1% tube loading can make resistivity of neat resin drops more than five orders. Electrical resistivity of MWNT/Epon862 composites decreases with the increase of tube loading. Also, good tube dispersion can help the formation of electrical conductive network. Electrical resistivity of random BP composite is as low as 3.92E-2 §Ùcm. The low resistivity of BP composites, BP/Carbon fiber(CF)/Epon862 composite and MWNT/CF/SC79 multi-scale composite make them very good candidates for EMI shielding materials. Show less

Date Issued

2005

Identifier

FSU_migr_etd-1258

Format

Thesis

Title

Characterization and Analysis of SWNT Buckypaper and Composite Actuators.

Since the discovery of Carbon Nanotubes in 1991, nanotechnology has come to a new episode. One of the new applications of single walled carbon nanotubes (SWNTs) is to develop high performance actuators. Nanotube actuation mechanism relies on quantum chemical expansion of graphitic carbon lattice if an additional electrical charge was applied. By electrochemical charging and discharging, a motion of carbon nanotubes can be generated. The phenomenon can be easily demonstrated on a free standing... Show moreSince the discovery of Carbon Nanotubes in 1991, nanotechnology has come to a new episode. One of the new applications of single walled carbon nanotubes (SWNTs) is to develop high performance actuators. Nanotube actuation mechanism relies on quantum chemical expansion of graphitic carbon lattice if an additional electrical charge was applied. By electrochemical charging and discharging, a motion of carbon nanotubes can be generated. The phenomenon can be easily demonstrated on a free standing film of SWNT buckypaper in an aqueous electrolyte. In this research, a setup was first established to accurately monitor actuation performance of SWNT buckypaper actuators. From a series of designed experiments, we found that the maximum deformation and applied voltage have a linear relationship. The actuation performance in varied electrolyte was also investigated. For alignment effect of SWNTs, it is the first time that we successfully performed a detailed characterization of the actuation performance of magnetically aligned buckypaper actuators. The aligned buckypaper actuators can demonstrate good response to electrical signal, showing very good repeatability and reversibility. In the experiments of using actuators with different dimensions, we found that larger surface area of SWNT actuators can create more deformation capacity, but it also made the actuator tip deflection unstable. In the high frequency response experiments, all of our SWNT actuator samples demonstrated good response to 1Hz and 10HZ square wave. The tip deflection of SWNT actuators decreased with the increases of electrical frequency. Finally, we developed a SWNT buckypaper/silver paint composite actuator for the first time. It can successfully respond to electrical signals. The results of this research provide essential data and information for further development and optimization of SWNT actuators. Show less

For developing high performance carbon nanotube-reinforced polymer composites, uniform nanotube dispersion, good nanotube/matrix wetting and interfacial bonding, controlled alignment and high tube loading are critical issues. A novel technical approach using a unique buckypaper/resin infiltration method has been developed at Florida Advanced Center of Composite Technologies (FAC2T) to fabricate nanocomposites with controlled tube dispersion, orientation, and high SWNT loading. Buckypapers are... Show moreFor developing high performance carbon nanotube-reinforced polymer composites, uniform nanotube dispersion, good nanotube/matrix wetting and interfacial bonding, controlled alignment and high tube loading are critical issues. A novel technical approach using a unique buckypaper/resin infiltration method has been developed at Florida Advanced Center of Composite Technologies (FAC2T) to fabricate nanocomposites with controlled tube dispersion, orientation, and high SWNT loading. Buckypapers are thin membranes or films of preformed networks of well-dispersed SWNTs. The preformed SWNT networks are eventually transformed in the nanocomposites to construct final nanostructures in the materials. Therefore, quality buckypapers are vital for developing high performance nanocomposites. This research focuses on systematically investigating buckypaper fabrication process and characterizing the resulting buckypapers for better understanding the process and building databases of both randomly oriented and magnetically aligned buckypaper materials. The results show that the formation of buckypaper during suspension filtration can be divided into three stages: free deposition, network formation and thickness build-up. Each stage has different filtration flow rate. The results also indicated that the average thickness, weight, and area density of the aligned buckypapers are smaller than that of the random buckypapers, while the average cubic density of the aligned buckypapers is higher than that of the random buckypapers. Due to possible re-assembly of nanotubes during magnetic alignment, the average rope size of the aligned buckypapers is larger than that of the random buckypapers, and its nanostructure also has relatively larger average pore size. Furthermore, the study of cleaning residual surfactant in the produced buckypapers was also conducted. The results show 70% of the surfactant can be removed by using the proposed cleaning method. Show less

In general, a minimum aberration criterion is used to evaluate fractional factorial designs. This dissertation begins with a comprehensive review and comparison of minimum aberration criteria definitions regarding their applications, relationships, advantages, limitations and drawbacks. A new criterion called the general balance metric, is proposed to evaluate and compare mixed-level fractional factorial designs. The general balance metric measures the degree of balance for both main effects... Show moreIn general, a minimum aberration criterion is used to evaluate fractional factorial designs. This dissertation begins with a comprehensive review and comparison of minimum aberration criteria definitions regarding their applications, relationships, advantages, limitations and drawbacks. A new criterion called the general balance metric, is proposed to evaluate and compare mixed-level fractional factorial designs. The general balance metric measures the degree of balance for both main effects and interaction effects. This criterion is related to, and dominates orthogonality criteria as well as traditional minimum aberration criteria. Besides, the proposed criterion provides immediate feedback and comprehensively assesses designs and has practical interpretations. The metric can also be used for the purpose of design augmentation to improve model fit. Based upon the proposed criterion, a method is proposed to identify the optimal foldover strategies for efficient mixed-level designs. The analysis of mixed-level designs involving qualitative factors can be achieved through indicator variables or contrast coefficients. A regression model is developed to include qualitative factor interactions which have been previously ignored. Show less

Photovoltaic (PV) systems behave in an extraordinary and useful way: they react to light by transforming part of the incoming photons into electricity. Since PV installations require no fuel to operate, produce no pollution while producing electricity, they require little maintenance and are modular. These unique properties make the technology a cost and energy-effective means of permitting a wide range of solar- electric applications. Thus, innovative design and manufacture of PV devices and... Show morePhotovoltaic (PV) systems behave in an extraordinary and useful way: they react to light by transforming part of the incoming photons into electricity. Since PV installations require no fuel to operate, produce no pollution while producing electricity, they require little maintenance and are modular. These unique properties make the technology a cost and energy-effective means of permitting a wide range of solar- electric applications. Thus, innovative design and manufacture of PV devices and equipment, offers a new vision for consumers and business as to how power can be provided. One such application involves the design and manufacture of a Solar-Powered Floating Fountain, including a robust design of experiment, performance, cost and safety analyses, is presented in this thesis. The uniqueness of the fountain manufactured for this research is the capability for aeration of stagnant water bodies, such as lakes and ponds. Aeration of these water bodies by using solar power is not only a new application of the renewable energy, but also, it provides an affordable method to promote biodiversity in stagnant ponds and lakes. The fountain was built by the Research Center for Cutting-Edge Technologies (RECCET) and installed on a pond at Innovation Park, Tallahassee. The system is composed of two pumps, an air compressor, six solar panels, kit of batteries, a linear current booster, pressurized water tank and the float. Aeration was by exposing the water to air through the nozzles on the tank. By using this technique, the lake gained dissolved oxygen in the lowest layer, accomplishing the main objective of this project. Statistical analysis using a Split Plot design showed a significant uptake of both dissolved oxygen and destratification. Show less

Carbon nanotubes (CNTs) are one of the wonders of modern science. Discovered a little over 15 years ago, they have shown the research community an outstanding set of properties. In terms of mechanical properties, they exhibit extremely high young's modulus, which, coupled with a high strain to break, leads to unsurpassed strength to break. CNTs also demonstrate superior thermal conductivity, good electrical capacity and high thermal stability. In light of these properties, CNTs are expected... Show moreCarbon nanotubes (CNTs) are one of the wonders of modern science. Discovered a little over 15 years ago, they have shown the research community an outstanding set of properties. In terms of mechanical properties, they exhibit extremely high young's modulus, which, coupled with a high strain to break, leads to unsurpassed strength to break. CNTs also demonstrate superior thermal conductivity, good electrical capacity and high thermal stability. In light of these properties, CNTs are expected to be introduced into a wide variety of new materials aimed at applications for various fields, such as high-performance composites, biological and chemical sensors, magnetic recording, nanoelectronic devices and flat panel displays. One such promising application is CNT-reinforced composite materials, exhibiting the possibility of outstanding mechanical properties. In practice, however, many reports indicate that nanocomposites are weaker or only slightly stronger than the neat resins. Several factors are believed to be the primary source of this discrepancy, namely poor nanotube dispersion in resin, inadequate alignment of the nanotubes, and weak interfacial bonding between nanotubes and resins. As a result, these have become crucial investigation issues for developing high-performance nanocomposites. In this dissertation, fundamental understanding of the interfacial phenomena between carbon nanotubes and polymer matrices are studied. Both molecular dynamics (MD) simulation, an effective approach to investigate nanoscale behaviors, and experimental investigation, are utilized to achieve this goal. First, we examine the interface formation phenomena between a Single Wall Carbon Nanotube (SWNT) and the resin, prior to curing, in the case of the Epon862 resin system. The MD simulation results outline the validity of some of the current theories, such as molecular migration and reduction of molecular mobility of the resin, while they seem to indicate some other mechanisms are not present in this resin system, such as molecular wrapping around the SWNTs. Second, existing MD simulation models of nanotube pullout are analyzed and modified to examine the energy of certain material systems more correctly, and to characterize interfacial shear strength in SWNT/polymer composites. The interfacial bonding and load transfer behaviors between the different SWNTs' configurations (open end, capped end, functionalized end) and three different matrices (polystyrene, polyethylene and Epon862) were examined using the modified models. The results of the modified models effectively reveal the effects of different tube configurations and resin matrices on the interfacial strength during a simulated pullout. Finally, we use MD simulation to investigate the coefficient of thermal expansion (CTE) of individual SWNTs, SWNT ropes, as well as SWNT nanocomposites. Experiments were also carried out in order to gain further insight in the results. It is found that, while the CTE of individual nanotubes is of low negative value, the CTE of the same tubes within a rope or a nanocomposite can significantly change. We also find that SWNTs can be utilized to tailor the CTE of the Epon862 resin system, depending on the functionalization of the SWNTs prior to their introduction in the resin. Finally, a new twisting vibration mode was revealed in SWNT ropes that should prove critical in further SWNT rope studies utilizing MD simulation. Show less

Date Issued

2006

Identifier

FSU_migr_etd-2739

Format

Thesis

Title

Polypyrrole as a Smart Material for Phosphate Contaminate Detection in Water.

Polypyrrole is a conductive polymer that has the potential to be used in many systems where conductivity can be studied. Polypyrrole when combined with a catalyst such as calcium acetate maybe able to provide a method of detecting phosphate in water systems. The hypothesis of this research explores the concept that a polypyrrole sensor could be manufactured via a casting method to produce a sensor that detects phosphates in water. Varying three primary factors produced a designed experiment... Show morePolypyrrole is a conductive polymer that has the potential to be used in many systems where conductivity can be studied. Polypyrrole when combined with a catalyst such as calcium acetate maybe able to provide a method of detecting phosphate in water systems. The hypothesis of this research explores the concept that a polypyrrole sensor could be manufactured via a casting method to produce a sensor that detects phosphates in water. Varying three primary factors produced a designed experiment and ANOVA analysis and comparison of means for three response variables: voltage, resistance and conductivity (calculated). Careful attention was paid to the values of the response variables across the geometry of the sensor prototypes. The sensor was evaluated for accuracy, sensitivity after multiple uses, and selectivity. After examining all of the data, the information obtained did not disprove the hypothesis, however it pointed to calcium acetate as the most powerful factor in the polypyrrole sensor in the accuracy test. Sensitivity and Selectivity tests had mixed findings. The samples not containing calcium acetate near the surface did not produce great changes in the response variables. The work presented in this thesis is an analysis of the raw data and materials used for generating the polypyrrole sensor prototype in order to introduce a new concept for manufacturing sensors using advanced materials; namely smart structures as sensors. Show less

In general, composite manufacturing processes have more variations compared to the metal manufacturing processes due to the larger raw material and manufacturing processes variations. Vacuum-assisted resin transfer molding (VARTM), one of a commonly used composite manufacturing processes, is becoming more popular due to its low cost tooling and environmental friendly operating conditions. Currently, most commercial products manufactured by VARTM are developed based on the user's experience... Show moreIn general, composite manufacturing processes have more variations compared to the metal manufacturing processes due to the larger raw material and manufacturing processes variations. Vacuum-assisted resin transfer molding (VARTM), one of a commonly used composite manufacturing processes, is becoming more popular due to its low cost tooling and environmental friendly operating conditions. Currently, most commercial products manufactured by VARTM are developed based on the user's experience and involve repeated experiments. To optimize the process, reduce manufacturing costs, and maintain consistent part quality, knowledge of mold filling, especially flow through thickness direction is required. This dissertation investigates the mechanism of the thickness variation and quantifies the magnitudes of the thickness distribution. Typically, thickness gradient and variations of VARTMed parts result from material variations and the infusion pressure gradient during the process. After infusion, certain amount of pressure gradient is frozen into the preform, which primarily contributes to the thickness variation. This research investigates the mechanism of the thickness variation dynamic change during the infusion and curing/relaxing processes. A numerical model was developed to track the thickness change of the bagging film free surface. A time-dependent permeability model as a function of compaction pressure was incorporated into an existing resin transfer molding code for obtaining the initial conditions of curing/relaxing process. Control volume (CV) and volume of fluid (VOF) methods were combined to solve the free surface problem. In addition, this dissertation analyzes the sources of the uncertainties and quantifies the magnitudes of the uncertainties by error propagation theory to characterize the statistical properties of the permeability values. Normal distribution and Weibull distribution were utilized as the statistical models for representing the average permeability values and race-tracking effects, respectively. Factors related to the part thickness variation were identified with design of experiments method and a better tooling design was obtained by configuring the different flow media. With the help of the simulation program, a process model-based tooling design optimization was formulated. However, the parameter uncertainty made the deterministic optimization unreliable. To address the issue of part-to-part thickness variation, a stochastic process simulation coupled with optimization was proposed and demonstrated. Show less

Date Issued

2006

Identifier

FSU_migr_etd-1440

Format

Thesis

Title

Comparative Analysis of the Power Output of Crystalline Photovoltaic (PV) Modules Using Solar Tracking System.

The focus of this thesis was to employ the use of two widely used types of photovoltaic (PV) modules namely monocrystalline and polycrystalline in a tracking system to determine which produces the greater output and compare these results to those reached by my predecessor, Michael O. Case[Case, 2003]. Several factors affect the overall productivity of a solar system. These include but are not limited to, time of day, time of year, latitude and atmospheric conditions, all of which were dealt... Show moreThe focus of this thesis was to employ the use of two widely used types of photovoltaic (PV) modules namely monocrystalline and polycrystalline in a tracking system to determine which produces the greater output and compare these results to those reached by my predecessor, Michael O. Case[Case, 2003]. Several factors affect the overall productivity of a solar system. These include but are not limited to, time of day, time of year, latitude and atmospheric conditions, all of which were dealt with throughout this thesis. The thesis began with the design and assembly of a solar tracking system. This system was used to collect data using monocrystalline and polycrystalline modules in various configurations. The configurations were stationary zero degrees, stationary forty degrees and solar tracking at forty degrees. Once data was acquired, it was entered in to the statistical software "Design Expert V6.0". Statistical analysis was then performed to determine the effect the chosen factors had on the power output of the two types of modules in terms of which type provides greater output and in what configuration. It was determined that the monocrystalline module produces greater power output than its polycrystalline counterpart. A final experiment was set up to determine the mode that produces the greatest power output. The results from the experiment revealed that monocrystalline modules deliver greater power in a tracking configuration. However, it may be necessary to consider the effects of temperature depending on application of these modules. Show less

Date Issued

2006

Identifier

FSU_migr_etd-0222

Format

Thesis

Title

Design and Analysis of Response Surface Designs with Restricted Randomization.

Many industrial experiments are conducted under various conditions which do not facilitate complete randomization of all the experimental factors. In response surface methodology whenever there are restrictions on randomization the experimental procedure usually follows the split plot design approach. Split plot designs are used when there are factors which are difficult or costly to change or adjust during an experiment. Split plot designs are currently generating renewed interest because of... Show moreMany industrial experiments are conducted under various conditions which do not facilitate complete randomization of all the experimental factors. In response surface methodology whenever there are restrictions on randomization the experimental procedure usually follows the split plot design approach. Split plot designs are used when there are factors which are difficult or costly to change or adjust during an experiment. Split plot designs are currently generating renewed interest because of their usefulness and practical application in industrial settings. Despite the work accomplished through various research efforts, there is still a need to understand the optimality properties of these designs for second-order response surface models. This dissertation provides the development of an analytical approach for the computation of various optimality properties for the assessment of second-order split plot designs. The approach involves a thorough investigation of the impact of restricted randomization on the information matrix, which characterizes much of the relationship between the design points and the proposed response surface model for split plot designs. Several important insights are presented for the construction of second-order split plot designs. In addition, the analytical equations reported compute exact design optimality values and are more efficient than currently available methods. A particular feature of these analytical equations is that they are functions of the design parameters, radius and variance ratio. Further, a significant result is the ability to efficiently compute the exact value of the integrated prediction variance for both split plot designs and completely randomized designs. The functionality of the computational procedures presented provides easy evaluation of the impact of changes in the design structure and variance ratio on the optimality properties of second-order split plot designs. Show less

Single walled carbon nanotubes (SWNTs) have demonstrated exceptional mechanical, thermal and electrical properties, and are regarded as one of the most promising reinforcement materials for the next generation of high performance structural and multifunctional composites with tremendous application potentials. However, to date, most application attempts have been hindered by several technical roadblocks, such as poor dispersion and weak interfacial bonding. Functionalization of nanotubes was... Show moreSingle walled carbon nanotubes (SWNTs) have demonstrated exceptional mechanical, thermal and electrical properties, and are regarded as one of the most promising reinforcement materials for the next generation of high performance structural and multifunctional composites with tremendous application potentials. However, to date, most application attempts have been hindered by several technical roadblocks, such as poor dispersion and weak interfacial bonding. Functionalization of nanotubes was suggested to be an effective way to overcome these technical issues and then to realize the full potential of nanotubes as reinforcement materials. In this dissertation, several original functionalization methods were proposed, studied, analyzed and quantitatively compared. These functionalization methods included precision sectioning of nanotubes using an ultra-microtome, electron-beam irradiation, amino-group grafting, and epoxide group grafting. Short nanotubes with open-ends show rich chemistry, ballistic transportation properties and capability of good dispersion. However, current reported cutting methods are difficult to protect tube sidewalls from devastation and to achieve desired length control. This research has developed a technique to precisely section aligned SWNT membranes through ultra-microtome in order to produce short and open-end tubes. Aligned SWNT membranes were sectioned to 50nm and 200nm. The results of AFM characterization and length statistical analysis have found the measured lengths were centered at 87nm and 246nm, respectively. Raman and TEM characterization results confirmed the minimized damage to the sidewalls. The cut-SWNTs were applied to nanocomposites fabrications. Young's modulus and strength of the composite were improved by 20% and 7%, respectively, when using 0.5wt% cut-SWNTs. The SEM results also confirmed the improvement in dispersion. The enhanced tensile strength indicates that load-transfer was improved due to the enhanced interfacial bonding. This dissertation also proposed a unique covalent sidewall functionalization through epoxy-grafting. The characterizations of Raman, FT-IR and TEM have proved the successful grafting of epoxide-group to the carbon nanotubes. The SEM results of the epoxy-grafted SWNTs reinforced composite indicated that significant improvement of dispersion was achieved. Dynamic Raman tests also revealed the considerable enhancement in the interfacial bonding. The tensile strength of nanocomposites was enhanced 27.1% and Young's modulus 30% with only 0.5wt% loading of epoxy-grafted SWNTs. When composites were fabricated with 1wt% loading of epoxy-grafted SWNTs, the strength and Young's modulus were improved by 40.3% and 60%, respectively. These substantial improvements are among the highest in the reported literatures. Furthermore, this research also succeeded in grafting amino-group onto SWNT sidewalls through one-step diazotization. Improvements in both dispersion and interfacial bonding were achieved. Young's modulus and strength for the amino-functionalized SWNTs composites with 0.5wt% loading were enhanced by 25% and 21.9%, respectively. The electron beam irradiation on the thin SWNTs membrane was both experimentally and theoretically investigated. Experimental results suggested that there exists a critical dose of irradiation in acquiring a desirable cross-linkage, above which significant enhancement of the SWNT membranes properties can be acquired. The theoretic modeling indicates that the density of cross-linkage is a quadratic function of the irradiation dosages. The irradiation-induced inter-tube bridging significantly enhanced the Young's modulus and tensile strength of the SWNTs membrane by 2 folds and 6 folds, respectively. Electric conductivity was also increased more than 1 fold. Both mechanical and electric properties improvements make the irradiated SWNT membranes very promising in the versatile applications, including electronic device, energy storage, biomaterials, and nanocomposites. All the methods developed in the dissertation demonstrated effectiveness in improving dispersion and interfacial bonding, resulting in considerable improvements in composite mechanical properties. Modeling of functionalization provided in-depth understanding and offered reasonable explanations of SWNTs length distribution, as well as carbon nanostructure transformation upon electron-beam irradiation. Both experimental and theoretical investigations would facilitate full realization of the potential of nanotubes-reinforced nanocomposites. Show less

Since the first Cathode Ray Tube (CRT) TV was invented in 1927, display technology has progressed at a rapid speed, attracting tremendous attention and enormous resources. Liquid Crystal Display (LCD) is the most mature and popular technology in flat panel displays compared to CRT. Carbon nanotube backlight unit (CNT-BLU) was regarded as a strong contender to replace the cold cathode fluorescence lamp backlight unit (CCFL-BLU) in LCD. CNTs have been spotlighted as one of promising... Show moreSince the first Cathode Ray Tube (CRT) TV was invented in 1927, display technology has progressed at a rapid speed, attracting tremendous attention and enormous resources. Liquid Crystal Display (LCD) is the most mature and popular technology in flat panel displays compared to CRT. Carbon nanotube backlight unit (CNT-BLU) was regarded as a strong contender to replace the cold cathode fluorescence lamp backlight unit (CCFL-BLU) in LCD. CNTs have been spotlighted as one of promising alternatives for new electron sources; small tips and large aspect ratios of CNTs allow for a large electric field enhancement that makes them ideal field emitters. In this research, nanotube network BuckyPaper was proposed to act as surface luminary source for BLU. The major objective of this research is to systematically characterize various field emission properties of BuckyPapers and various lengths of open-ended CNTs. Particularly, low turn-on voltage, high average current, high luminance, low power consumption, uniformity and longer life-span will be explored. VGCNF/SWNT in ratio 1:1 BuckyPaper film demonstrated the lowest turn-on voltage (0.623 V/um) and randomly dispersed SWNT BuckyPaper film showed the largest enhancement factor value (1062) among all BuckyPaper samples. The structure of emitters might be the major reason for the varying results from different compositions of BuckyPaper films. The 400 nm open-ended SWNT paste showed the lowest turn on voltage at 0.313 V/um and the largest enhancement factor value (3470). Open-ended SWNT paste exhibited the best I-V properties, but did not demonstrate acceptable durability. The effect of varying aspect ratio of open-ended SWNT will be investigated in the future. Show less

Date Issued

2006

Identifier

FSU_migr_etd-3858

Format

Thesis

Title

Integrated Robust Design Using Computer Experiments and Optimization of a Diesel HPCR Injector.

Robust design has been gaining plenty of attention in both academia and industry over the past two and half decades. However, there is still plenty of room for improvement. In this dissertation research, several drawbacks of the existing robust design methods were identified and analyzed. These shortcomings mainly include incompatible robust parameter design and tolerance design optima, inadequate attention to internal noise factors, limitation of Steepest Descent search in parameter design... Show moreRobust design has been gaining plenty of attention in both academia and industry over the past two and half decades. However, there is still plenty of room for improvement. In this dissertation research, several drawbacks of the existing robust design methods were identified and analyzed. These shortcomings mainly include incompatible robust parameter design and tolerance design optima, inadequate attention to internal noise factors, limitation of Steepest Descent search in parameter design process, limitation of robust design using computer experiments, limitation with the Loss Function, and insufficient connection between the academia and industry on robust design. An integrated robust design framework was proposed to help achieve robustness against both external and internal noises. A Steepest Descent Driven Parameter Design method was developed to enhance parameter design. Also developed was an improved loss function for robust tolerance design. The proposed methodology was applied using computer simulation experiments to optimize the design of a state-of-the-art injector in a High Pressure Common Rail (HPCR) injection system in a diesel engine. The injector simulation model was built using Advanced Continuous Simulation Language (ACSL) and well calibrated through extensive hardware experiments. iSIGHT, an integration and optimization software package, was utilized to assist the computer experiments. Design Experts and Minitab were used to conduct statistical designs and analysis. It was demonstrated that the injector performance was significantly improved with the proposed method. The proposed method was also compared with Taguchi's method and Response Surface Methodology based robust design method. Show less

Date Issued

2006

Identifier

FSU_migr_etd-2486

Format

Thesis

Title

An Agency Approach to Analyze and Improve a Photometric Device Test Procedure Using Design of Experiments Methodology.

Proper function of traffic photometric devices such as traffic signal modules is crucial for safe operation in the traffic environment. The Traffic Engineering Research Lab (TERL) of Florida Department of Transportation (FDOT) has a significant role in ensuring that these devices perform in accordance to specified standards at all times. Therefore it is necessary that this lab is equipped with the right kind of test facility and procedures, thus enabling device performance verification be... Show moreProper function of traffic photometric devices such as traffic signal modules is crucial for safe operation in the traffic environment. The Traffic Engineering Research Lab (TERL) of Florida Department of Transportation (FDOT) has a significant role in ensuring that these devices perform in accordance to specified standards at all times. Therefore it is necessary that this lab is equipped with the right kind of test facility and procedures, thus enabling device performance verification be done periodically in addition to new device qualifications. The Institute of Transportation Engineers (ITE) specification is used as one of the governing documents. This research will describe an investigation performed upon the test procedure for light emitting diode (LED) signal modules. The purpose of the investigation was to identify variability in procedure activities and to determine the overall test procedure primarily using design of experiments methodology and other statistical analysis approaches. Data analysis by this methodology was essential to characterize process variability because the test procedure execution requires management of six input factors which were not previously tested for significance. Findings from this work are also used to recommend to the lab management on issues about potential facility upgrades. Recommendations were also provided to the ITE to explore the validity of their data from statistical perspective. This research improved the test procedure for testing LED signal modules which will permit further determination of other photometric devices test procedures. Show less

As wireless devices become more prevalent, the radio frequency (RF) spectrum is becoming more densely populated with cell phone and internet related broadband activities (e.g. text messaging, web browsing, and wireless routing). This feasibility study presents a sensitivity study on how location, use of an antenna and motion may impact the ability to measure RF power density for specific frequencies. The RF power obtained from a nearby radio station was compared to the relative RF power... Show moreAs wireless devices become more prevalent, the radio frequency (RF) spectrum is becoming more densely populated with cell phone and internet related broadband activities (e.g. text messaging, web browsing, and wireless routing). This feasibility study presents a sensitivity study on how location, use of an antenna and motion may impact the ability to measure RF power density for specific frequencies. The RF power obtained from a nearby radio station was compared to the relative RF power available for frequencies understudy. The results of the study indicated that 2.4 GHz is significant in terms of prevalence and power density which allows for technological opportunity and caution due to potential health hazards. Optimization of a 2D inductor is also presented and which makes it easier for RF inductor designers to selectively choose the dimensions and number of turns of the inductor based on the desired inductance and power. Show less

Single-walled carbon nanotube buckypaper (SBP) is a thin film of preformed nanotube networks that possesses many excellent properties. SBP is considered to be very promising in the development of high-performance composite materials; however, the high cost of single-walled nanotubes (SWNTs) limits industrial applications of SBP materials. Mixed buckypaper (MBP) is a more affordable alternative that combines SWNTs with low-cost multi-walled nanotubes (MWNTs) or carbon nanofibers (CNFs) to... Show moreSingle-walled carbon nanotube buckypaper (SBP) is a thin film of preformed nanotube networks that possesses many excellent properties. SBP is considered to be very promising in the development of high-performance composite materials; however, the high cost of single-walled nanotubes (SWNTs) limits industrial applications of SBP materials. Mixed buckypaper (MBP) is a more affordable alternative that combines SWNTs with low-cost multi-walled nanotubes (MWNTs) or carbon nanofibers (CNFs) to retain most of the excellent properties of SBP while significantly reducing the cost. This study proposes a manufacturing process of MBPs. The process parameters were studied through experimental design and statistical analysis. The parameters included mixing material type, mixing ratio, sonication effect, surfactant amount, and cleaning effect. The effects of the parameters on nanostructure uniformity, purity, Brunauer-Emmett-Teller (BET) surface area and electrical conductivity of the resultant MBPs were revealed. Results of the study show that all those parameters and their interactions are influential to the dispersion and uniformity of nanostructure and purity, but only mixing material type and ratio are influential to the BET surface area and electrical conductivity. To systematically reveal the process-nanostructure-property relationship of SBP and MBP materials, the nanostructures of the buckypapers were characterized as rope size, length and pore size distributions of the nanomaterials in resultant buckypapers. These distributions featured bimodal phenomenon due to different material mixtures; therefore, the distributions were further separated into two individual ones and fitted into Weibull distributions. Two nanostructure-property models of buckypaper materials were developed. The specific surface area model was built upon the characterization and analysis of buckypaper nanostructures. The model showed that rope size distribution and mixed ratio of nanomaterials are governing factors for the resultant specific surface area of buckypaper. The electrical conductivity model captured multiscale electrical transport phenomenon of nanotube networks in buckypapers. The model considered chirality, contact area, contact type, diameter, length and orientation distributions of nanotubes in buckypapers. The proposed models not only can predict property trends correctly, but can also reveal the critical process-nanostructure-property relationships of buckypaper materials. The results are important for the further tailoring and optimization of the manufacturing process and properties of nanotube buckypapers. Show less

Many researchers proposed the use of carbon nanotubes as an advanced metal catalyst support for electrocatalysis applications. In this research, buckypaper (thin film of preformed nanotube network) electrodes with different weight ratios of carbon nanomaterials, including SWNT, MWNT, CNF, and Vulcan XC-72 (CB), were fabricated and compared by their electrochemical properties using cyclic voltammetry (CV) test. Platinum (Pt) nanoparticles were successfully electrodeposited on the mixed... Show moreMany researchers proposed the use of carbon nanotubes as an advanced metal catalyst support for electrocatalysis applications. In this research, buckypaper (thin film of preformed nanotube network) electrodes with different weight ratios of carbon nanomaterials, including SWNT, MWNT, CNF, and Vulcan XC-72 (CB), were fabricated and compared by their electrochemical properties using cyclic voltammetry (CV) test. Platinum (Pt) nanoparticles were successfully electrodeposited on the mixed buckypapers in mixed ethylene glycol, H2PtCl6, and H2SO4 aqueous solutions by applying a potential pulse at 0.2 and -0.25 V, forming Pt/mixed buckypaper electrodes. The dispersion and particle size of Pt nanoparticles on the buckypapers were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The average diameter of Pt nanoparticles on the buckypapers was 10 nm. Surface areas of the Pt nanoparticles on the mixed buckypapers were determined by cyclic voltammogram measurements in 0.5 M H2SO4 solution, and electrocatalytic performances of the resultant buckypaper electrodes were observed. Compared to the Pt/CB electrodes, the Pt/SWNT+MWNT buckypaper electrode exhibits higher electrocatalytic performance. The highest electrochemical surface area (ECSA) of Pt/SWNT+MWNT (1:3) electrodes reaches 43.7m2/g and is about 1.6 times higher than that of the Pt/CB electrode. This may be attributed to the small particle size and good dispersion of platinum, high conducting property of carbon nanotubes, special deposition phenomenon, and unique three–dimension electrode structure. The research results suggest that mixed buckypapers are good candidates for catalyst supports in fuel cell applications because of their high electrocatalytic performance. The reduction of the amount of precious metal catalyst (Pt) needed is important for real-world applications. Further research into the optimization of Pt deposition and nanostructure of mixed buckypapers could lead to highly efficient and potentially affordable electrodes for fuel cell applications. Show less

Date Issued

2007

Identifier

FSU_migr_etd-2959

Format

Thesis

Title

Development of Continuous Manufacturing Process for Magnetically Aligned and Random Nanotube Buckypaper.

Fiber-reinforced composites are becoming more popular due to their high strength to weight ratio, making them a suitable replacement for traditional metals for lightweight applications. However, for applications where electro-conductivity and thermo-conductivity are required, fiber-reinforced composites lack the necessary properties without adding parasitic components. As a result of extensive research, high performance carbon nanotube-reinforced composites are considered as one of the key... Show moreFiber-reinforced composites are becoming more popular due to their high strength to weight ratio, making them a suitable replacement for traditional metals for lightweight applications. However, for applications where electro-conductivity and thermo-conductivity are required, fiber-reinforced composites lack the necessary properties without adding parasitic components. As a result of extensive research, high performance carbon nanotube-reinforced composites are considered as one of the key solutions to this issue, with buckypapers serving as the central constituent. Buckypapers are thin membranes of well-dispersed networks of nanotubes held together by van der Waals forces. Buckypapers are considered as one of the promising candidates for incorporating nanotubes into composite manufacturing due to their ease of handling and the ability to transfer the properties of the nanotubes into the resultant composites. Buckypapers enable thermal and electro-conductivity in ranges not possible using fiber composites alone. The objective of this research is to develop an effective, affordable manufacturing process capable of continuously fabricating buckypaper materials to meet market demands, as well as property and quality requirements from the consumers. The batch method of buckypaper manufacturing processes have been investigated and standardized by previous studies. Successful results under the standardized process have been adopted to pilot buckypaper production. Such studies have also attracted the interest of industrial consumers who require large-scale manufacturing, and continuity of buckypaper materials, which are not offered by the current batch method. Through the development of four generations of prototypes, this research has successfully designed and fabricated the Nano Material Continual Integration System (NM-CIS), a filtration system capable of producing high quality continuous buckypaper materials. A prototype to produce continuous 1.5in wide buckypapers of randomly-dispersed SWNTs has been successfully developed. Furthermore, the research has characterized the physical and electrical properties and compared them with current batch-production buckypapers. The results indicate that the continuous manufacturing processes have the potential to scale-up production of continuous buckypaper products to achieve desired quality, continuity and affordability for potential industrial applications. Furthermore, the research has designed and fabricated the MA-CIS system to fabricate continuous magnetically aligned buckypaper materials, and the W-CIS system to produce 11-in wide-buckypaper Show less

Date Issued

2007

Identifier

FSU_migr_etd-1466

Format

Thesis

Title

Experimental Study of Electrical Conductivity of Carbon Nanotube, Nanofiber Buckypapers and Their Composites.

The discovery of carbon nanotubes brought on a whole new world of nanotechnology. Various forms of carbon materials were developed, including single-walled carbon nanotube (SWNT), multi-walled carbon nanotube (MWNT), and carbon nanofiber (CNF). These carbon nanomaterials attract academic and industrial interests because of their exceptional mechanical, thermal and electrical properties. For electrical conductivity in particular, it is widely recognized that SWNTs have considerable potential... Show moreThe discovery of carbon nanotubes brought on a whole new world of nanotechnology. Various forms of carbon materials were developed, including single-walled carbon nanotube (SWNT), multi-walled carbon nanotube (MWNT), and carbon nanofiber (CNF). These carbon nanomaterials attract academic and industrial interests because of their exceptional mechanical, thermal and electrical properties. For electrical conductivity in particular, it is widely recognized that SWNTs have considerable potential as building blocks for future nanoscale electronics and conducting composites. The first objective of this thesis is to develop a comprehensive electrical resistivity measurement system which can measure the electrical resistivity of nanotube-based materials ranging from 1.0E-6 ''cm to 1.0E+17 ''cm. The test setup performance was examined using Gage R and R (Repeatability and reproducibility) analysis. The second objective is to characterize and analyze electrical conductive properties of different Buckypapers (thin film of nanotube network) and nanocomposites to demonstrate their performance and establish a database for future applications. Detailed characterizations of the electrical conductivities of SWNT, MWNT, and carbon fiber Buckypapers and their composites were conducted. The influential factors of resistivity of Buckypapers were discussed, including the effects of nanotube batches, processing methods, and surfactant types. In this study, the electrical resistivity properties of the mixed Buckypapers of SWNT/MWNT and SWNT/CNF were also investigated. The effects of nanoparticle types (SWNT, MWNT, and CNF) were examined. The results show that the low cost MWNT and nanofiber materials can still retain good electrical conductivity of the resultant mixed Buckypapers, creating excellent application potentials for developing cost effective multifunctional composites. The thesis also studied the electrical conductivity of functionalized SWNT Buckypapers. Functionalization of nanotubes was suggested to be an effective way to tune the electrical conductivity of CNTs. The functionalization methods included electron-beam irradiation and fluorinated grafting. The resistivities of the functionalized SWNT Buckypapers were experimentally investigated. Show less

Date Issued

2007

Identifier

FSU_migr_etd-7081

Format

Thesis

Title

The Utilization of Formable Paint Films in the Implementation of in-Mold Decoration of Composites Manufactured by the Resin Infusion Between Double Flexible Tooling Process.

With the rapidly increasing deployment of polymer composites as the material of choice, environmentally benign methodologies for manufacturing and coating the resulting components are imperative. Several methodologies are currently in use to manufacture composites in 'closed' molds; however, the implementation of coatings is still for the most part, done using methods that provide for the release of harmful, volatile organic compounds (VOC) into the environment. The current work details the... Show moreWith the rapidly increasing deployment of polymer composites as the material of choice, environmentally benign methodologies for manufacturing and coating the resulting components are imperative. Several methodologies are currently in use to manufacture composites in 'closed' molds; however, the implementation of coatings is still for the most part, done using methods that provide for the release of harmful, volatile organic compounds (VOC) into the environment. The current work details the utilization of a thermo-formable polycarbonate paint film for the in-mold decoration (IMD) of composite materials manufactured using the novel Resin Infusion between Double Flexible Tooling (RIDFT) process. RIDFT is a vacuum driven process where resin infusion is performed between two reinforcement-filled flexible diaphragms. Upon completion of infusion, the flexible diaphragms are vacuum formed over a one-sided tool, providing for the rapid cost effective manufacture of composite components. In this process, in-mold decoration is achieved by including a thermo-formable polycarbonate paint film within the flexible diaphragms, over the reinforcing fabrics (fibers), prior to infusion. After infusion, the whole assembly (paint film, fibers and resin) is vacuum formed to the desired geometry, thus achieving in-mold decoration. The inclusion of a polycarbonate film to the RIDFT process required a comprehensive analysis on forming capability vs. surface quality finish of the composite assembly. With increasing temperature, better draw ability was achieved; however, print-through of the fibers through the film occurred. Several process parameters were optimized through sequential experimentation using analysis of variance (ANOVA) in terms of print-through, as the response variable. High and low levels of five controllable factors (temperature, mold type, time, fiber reinforcement, and vacuum pull) were tested. Light scatter, caused by irregular surfaces, was quantified through the use of Matlab, allowing for precise response input values. Statistical validation proved minimal print-through at a forming temperature of 147' C; however, at this temperature formability of the film was limited to subtle contours. At 160' C, the forming capability of the composite assembly was maximized, yet, surface finishes exhibited high print-through. This thesis describes achievements, difficulties, and future work in the utilization of polycarbonate films for RIDFT in-mold decoration. Show less

Advanced composites which offer robust mechanical properties are being increasingly used for structural applications in the aerospace, marine, defense and transportation industries. However, the anisotropic nature of composite materials leaves it susceptible to problematic failure; the development of means for detecting failure is imperative. As design and functionality requirements of engineering structures such as spacecraft, aircraft, naval vessels, buildings, dams, bridges and ground... Show moreAdvanced composites which offer robust mechanical properties are being increasingly used for structural applications in the aerospace, marine, defense and transportation industries. However, the anisotropic nature of composite materials leaves it susceptible to problematic failure; the development of means for detecting failure is imperative. As design and functionality requirements of engineering structures such as spacecraft, aircraft, naval vessels, buildings, dams, bridges and ground-based vehicles become more complex; structural health monitoring (SHM) and damage assessment is becoming more rigorous. Though structures involved have regular costly inspections, the damage associated with composites in SHM systems can lead to catastrophic and expensive failures. Industry and research have no single technique used on its own to provide reliable results. Integrating several nondestructive evaluation (NDE) techniques could provide a solution for real-time health monitoring. Such studies, utilizing acoustic emission (AE), A-scans, C-scans, and laser shearography have reported considerable success. Nevertheless, damage detection has to be reliable and cost effective. The answer may lie with the development of SHM systems by the use of triboluminescent crystals, as well as optical fibers embedded in the composite matrix. These crystals react to straining or fracture by emitting light of varied luminous intensity. Thus, a fiber-reinforced plastic (FRP) laminate doped with Triboluminescent (TL) or Mechanoluminescent (ML) crystals, acting as health sensors to its host material, will give an indication of crack initiation well ahead of catastrophic failure(s). The development of an in-situ health monitoring system for safety critical structures is a viable route through 'Triboluminescence'. Assessing the viability of a proposed structural sensor system requires cross-linking between key areas in science and engineering. Initial testing has shown that light can propagate through doped resins alone, as well as doped FRP laminates. The luminous intensities relation to impact velocity adds credence to a monitoring system that can characterize impact activity. However, Triboluminescent crystals have high material density. In response, a two-dimensional rotational mold was built to counteract massive settling under normal vacuum molding processes. Micro-structural evaluations using scanning electron microscopy (SEM) and EDAX imaging have aided in demystifying particulate dispersion of TL fillers through use of image processing. Show less

Micro air vehicles (MAVs) are small scale unmanned aerial vehicles (UAVs) that are used for reconnaissance, intelligence gathering and battle damage assessment. The U.S. Air Force Research Lab Munitions Directorate develops MAVs for various defense missions. The case involves a tandem wing MAV that is designed to have retractable wings for transport, control surfaces on the aft wing, and two different vertical tail configurations. Wind tunnel testing is one of the vital steps in MAV... Show moreMicro air vehicles (MAVs) are small scale unmanned aerial vehicles (UAVs) that are used for reconnaissance, intelligence gathering and battle damage assessment. The U.S. Air Force Research Lab Munitions Directorate develops MAVs for various defense missions. The case involves a tandem wing MAV that is designed to have retractable wings for transport, control surfaces on the aft wing, and two different vertical tail configurations. Wind tunnel testing is one of the vital steps in MAV development for evaluating and ensuring that stability and control requirements are met for sustained flight. Traditionally, wind tunnel tests have been performed using a one factor at a time (OFAT) approach. Wind tunnel OFAT involves testing at many levels of one particular factor, usually angle of attack (AoA), while holding all other input factors constant; this technique is then repeated for various input factor configurations. This classic approach can be useful in determining the effect that each input alone has on the desired response. However, OFAT is not capable of identifying the influence that inputs interacting with one another have on the response, which commonly affect aircraft performance. Furthermore, OFAT is not capable of characterizing uncertainty that is present in experimentation. The research objective is to develop a testing strategy that provides an efficient number of test points to run in the wind tunnel effectively characterizing the aerodynamic behavior of MAVs as a function of design changes, changes in attitude and control inputs, while reducing costs and resources using design of experiments (DOE) and response surface methods (RSM). The research involves one of the first applications of second-order split plot designs, as well as the traditional completely randomized design. The DOE/RSM approach will be directly compared to the traditional OFAT wind tunnel testing that is performed during the same test period. The analyses resulting from the DOE/RSM approach will highlight its capabilities in identifying factor interactions, characterizing system uncertainty, and providing stability and control analyses – the common objectives of wind tunnel testing. The outcome of the study will demonstrate the effectiveness of DOE/RSM techniques when tailored to meet the specifications of wind tunnel testing. Some characteristics involved with the wind tunnel environment are low noise, qualitative factors, hard-to-change factors, and second-order models. The collaboration of experimental design techniques adapted to traditional wind tunnel testing techniques will provide a powerful approach to characterizing and optimizing aerodynamic systems. Show less

Polycarbonate (PC) is a transparent, impact resistant polymer that provides protection against breakage or intrusion. The mechanical toughness of PC is reported to be associated with the molecular motion of main chain molecules. The molecular motion is present upon exposure to impact and can therefore provide efficient dissipation of impact energy. PC has found wide usages in military and commercial applications. This thesis investigates processing and characterization of transparent PC... Show morePolycarbonate (PC) is a transparent, impact resistant polymer that provides protection against breakage or intrusion. The mechanical toughness of PC is reported to be associated with the molecular motion of main chain molecules. The molecular motion is present upon exposure to impact and can therefore provide efficient dissipation of impact energy. PC has found wide usages in military and commercial applications. This thesis investigates processing and characterization of transparent PC/carbon nanotube (CNT) composite films. The reinforcing capability and efficiency of CNTs in nanocomposites have been studied intensely world-wide due to their exceptional mechanical properties. Not only do they provide stiffness and strength, but they also have been reported to impart fracture toughness when dispersed in polymer matrices. As cracks develop in nanocomposites, CNTs serve as the bridging nanofibrils that effectively retard crack propagation. In some cases, CNTs act as obstacles that obstruct the crack propagation paths, thus increasing the energy needed to be dissipated for further crack opening. This research deals with two important issues in multi-walled carbon nanotube (MWNT)-based composites that are seemingly trade-offs – dispersion of high-loading MWNTs and maintenance of optical transparency. Higher loading of MWNTs is desired for increased reinforcing effects; however, it is limited by the difficulties in achieving uniform dispersion in the polymer resin due to increased viscosity and the tendency of MWNTs to aggregate. At the same time, only a small addition of MWNTs (less than 1 wt.%) makes the resin turn dark, which defeats the advantage of the transparency that should otherwise be retained by PC. PC/MWNT composite films (up to 0.15 wt.% MWNT) were fabricated using a solvent-based film casting method. Several optimization schemes were adopted to determine the most suitable solvent and the concentrations of PC/MWNT in the solvent. Solvent-induced PC crystallization, which was evidenced by milky tinting in the produced films, was minimized by identifying and optimizing the process parameters, namely, PC/MWNT/solvent solution viscosity, casting temperature, and film thickness. Design of experiments technique was used to determine the combination of optimal parameters. Show less

Date Issued

2007

Identifier

FSU_migr_etd-3811

Format

Thesis

Title

Development and Parametric Studies of Carbon Nanotube Dispersion Using Electrospraying.

Since the discovery of carbon nanotubes in the early 1990s, a new era in nanotechnology opened up, impacting both scientific and technological fronts. One of the key challenges in processing of carbon nanotube-based materials and structures is proper dispersion of the nanoconstituents. Fundamental roadblocks to maximumize utilization of the exceptional properties of carbon nanotubes are their tendency to aggregate due to intermolecular forces and the resulting difficulties in dispersing them... Show moreSince the discovery of carbon nanotubes in the early 1990s, a new era in nanotechnology opened up, impacting both scientific and technological fronts. One of the key challenges in processing of carbon nanotube-based materials and structures is proper dispersion of the nanoconstituents. Fundamental roadblocks to maximumize utilization of the exceptional properties of carbon nanotubes are their tendency to aggregate due to intermolecular forces and the resulting difficulties in dispersing them into individual tubes. In this study, a novel carbon nanotube dispersion technology that uses electrospraying was developed, analyzed, and evaluated. We established image analysis based measurement that can be used to quantify the degree and uniformity of carbon nanotube dispersion, and performed a series of designed experiments. Rigorous statistical analyses were conducted to investigate the parametric effect of electrospraying, and the design of experiments based models were derived. As validated through experiments, the design of experiments models can serve as effective guidelines for selecting the electrospraying parameters that allow controlled nanoparticle dispersion. Carbon nanotube electrospraying is expected to be applicable to a broad range of technical fields, owing to its low cost, ease of implementation, environmental friendliness, and scalability for industry use. Potential applications include, transparent, conductive carbon nanotube coating for flexible displays, multiscale carbon nanotube patterning, and continuous nanocomposite processing, the proofs-of-concept of which have been demonstrated in this study. Show less

Non-metallic materials such as ceramics are an accepted method to produce armor systems due to their low density, high hardness, high rigidity and strength in compression. Due to ceramic's low fracture toughness and the tendency of fracturing when subject to high tensile stresses, a back-plate of a more ductile material such as aluminum, steel or fiber reinforced plastics have be used to keep the laminate intact when subjected to a projectile impact. Ceramic plates have the ability to... Show moreNon-metallic materials such as ceramics are an accepted method to produce armor systems due to their low density, high hardness, high rigidity and strength in compression. Due to ceramic's low fracture toughness and the tendency of fracturing when subject to high tensile stresses, a back-plate of a more ductile material such as aluminum, steel or fiber reinforced plastics have be used to keep the laminate intact when subjected to a projectile impact. Ceramic plates have the ability to initially slow down the bullet; then break it down into smaller fragments, but are not meant to fully stop the projectile. The ceramic plate reduces the bullets capacity to penetrate and transfer the kinetic energy from the projectile to the plate. This disperses the energy throughout a larger area thus absorbing most of the impact energy. The ceramic plate requires a backing plate for support to compensate for the brittle nature of the ceramic materials. The backing plate must be capable of containing any stray fragments and absorb some of the residual energy. The downside to this system is the total weight of the system is too large. Fiber reinforced composites have been used increasingly to replace heavier metal structures because of their high stiffness to weight ratios, corrosion resistance, damage tolerance, and functional integration. As such, new advanced fiber composites are now replacing aluminum components in the aerospace industry. Furthermore, the failure modes of composites promote pronounced energy absorption especially under high speed impact loading. This attribute has made composites valuable materials for the defeat of projectile impact and they are now increasingly being used in personnel armor like the Small Arms Protection Insert (SAPI). The current work stems form the need of the US Air Force Pararescue Jumpers (PJ). Their current SAPI equipment is a pure polymer (UHMWPE) solution that defeats the 7.62 mm rounds at muzzle velocities over 2500 ft/sec. They are however thick and heavy, making their use rather precarious in some instances. As such, a thinner, lighter and durable system is desired that retains the same properties as the current system. This work set out to investigate the viability of producing thinner and lighter cost effective plates for the defeat of the 7.62 mm rounds at muzzle velocities and criteria set by the PJSAPI specifications. The manufacturing of these plates could have a large impact on the performance of the material. Preliminary tests show that the increase in pressure applied to the laminate can increase the overall performance with a decrease in the overall weight of the system. Show less

Since carbon nanotubes (CNTs) were first discovered in 1990, many researchers have been striving to learn more about their remarkable mechanical and physical properties. With these exceptional properties, CNTs are considered by researchers as an ultimate reinforcement material for composite applications. However, many reports indicate that nanotube/epoxy composites are weaker or only slightly stronger than neat epoxy resins. This has been found to be primarily due to a combination of several... Show moreSince carbon nanotubes (CNTs) were first discovered in 1990, many researchers have been striving to learn more about their remarkable mechanical and physical properties. With these exceptional properties, CNTs are considered by researchers as an ultimate reinforcement material for composite applications. However, many reports indicate that nanotube/epoxy composites are weaker or only slightly stronger than neat epoxy resins. This has been found to be primarily due to a combination of several factors, namely poor tube dispersion, inadequate alignment and weak interfacial bonding. In this study we focused on improving mechanical properties of nanocomposites and nanotube/carbon fiber multiscale reinforcement composites by improving nanotube dispersion and alignment. In order to improve dispersion, it is necessary to quantify tube dispersion quality first. We proposed a quantitative method by using Differential Scanning Calorimeter (DSC) to quantify tube dispersion uniformity in tube/resin mixtures. The preliminary result shows that this method is able to characterize the dispersion quality numerically. The previous dispersion technique was also investigated and modified through the use of a Design of Experiment (DOE) to improve the tube dispersion quality in Epon 862 resin. Results indicate that the tensile modulus of 0.5wt% nanocomposites has 26.5% improvement over that of the neat resin. This improvement is four times higher than that of 0.5wt% nanocomposites made by the previous tube dispersion technique. This modified tube dispersion technique was also used to manufacture multiscale nanocomposites to enhance through-thickness properties. The results also demonstrate that with the addition of 0.12wt% single-walled nanotubes (SWNTs), the storage modulus, tensile modulus and tensile strength of multiscale nanocomposites have a 16.74%, 0.6% and 3.8% increase over that of conventional fiber-reinforced composites. In order to further improve the mechanical performance of nanocomposites and multiscale nanocomposites, studies were carried out to align nanotube and nanofiber in nanocomposites and multiscale nanocomposites using an 8.5T magnetic field. Even though a certain degree of tube alignment was observed by means of Raman spectroscopy, the obvious improvement of mechanical properties of aligned nanotube and nanofiber/resin nanocomposites was not obtained, due to low tube loading and high viscosity issues. However, the property improvement of aligned multiscale nanocomposites was observed. The short-beam shear (SBS) strength of 0.04wt% aligned SWNT multiscale nanocomposites showed a 13.05% increase over that of randomly oriented multiscale nanocomposites when the SWNTs were aligned along the through-thickness direction. The effect on the Tgs of nanocomposites when adding nanotubes was also investigated. Show less

Date Issued

2007

Identifier

FSU_migr_etd-1382

Format

Thesis

Title

Of Engineering Augmenting Second Order Designs for Model Validation and Refinement.

Validation is an important step that is often left out of modeling due to lack of time, lack of funding, or just plain ignorance. Many industries that practice design of experiments leave out this important step because the benefits are not visible for the model that is often created. In addition, there appears to be no clear way to measure whether or not the validation points truly validate the model. This paper focuses on a new way of validation that will both refine the model, yielding... Show moreValidation is an important step that is often left out of modeling due to lack of time, lack of funding, or just plain ignorance. Many industries that practice design of experiments leave out this important step because the benefits are not visible for the model that is often created. In addition, there appears to be no clear way to measure whether or not the validation points truly validate the model. This paper focuses on a new way of validation that will both refine the model, yielding more information, and validate the model. This new approach of validation is a simple way of improving the model and making sure that it does what it was designed to do. This validation procedure is only used for 2nd order models that are based off of a central composite design, but have the possibility of picking up 3rd order terms that the model was unable to identify without the extra validation points. Validation points are chosen through a genetic algorithm using space-filling and orthogonality criteria. A new set of points that is different from that of the design is derived. These points are better than just randomly selecting points that have no meaning. Validation is a necessary step to eliminate many risks. The procedure defined here is useful for determining 3rd order terms and their validity in a model. Show less

This research focuses on the third-order response surface designs for global optimization and mapping of systems or processes. The current second-order response surface designs may not be accurate and efficient enough to describe the true model of the systems or processes in terms of multiple design criteria. This research addresses the needs for third-order designs by identifying corresponding inaccuracy issues and attempts to create efficient designs by investigating different ways of... Show moreThis research focuses on the third-order response surface designs for global optimization and mapping of systems or processes. The current second-order response surface designs may not be accurate and efficient enough to describe the true model of the systems or processes in terms of multiple design criteria. This research addresses the needs for third-order designs by identifying corresponding inaccuracy issues and attempts to create efficient designs by investigating different ways of building third-order models. This research proposes functionality as a new design property to guide the comparison of practicability and ease of use of different designs. Furthermore, it looks into generating multiple criteria optimal third-order designs for continuous cuboidal region using NSGA-II algorithm. IV-optimality and space filling have been selected as the two primary objectives for this multiple criteria third-order design problem. This research shows that the NSGA-II does not provide the results as expected for third-order designs, and nested faced centered design is the best overall design in IV-optimality, space filling, orthogonality and functionality. A Pareto-optimal front is given to satisfy different practitioners' needs. Show less

Environmental and economic problems caused by over-dependence on fossil fuels have increased the demand and request for green energy produced by alternative renewable sources. Producing electricity by using photovoltaic cells (also called solar cells) is a fast growing industry. There are two main ways to make photovoltaic cells more efficient. One method is to improve the materials design and the other is to optimize the output by installing the solar panels on a tracking base that follows... Show moreEnvironmental and economic problems caused by over-dependence on fossil fuels have increased the demand and request for green energy produced by alternative renewable sources. Producing electricity by using photovoltaic cells (also called solar cells) is a fast growing industry. There are two main ways to make photovoltaic cells more efficient. One method is to improve the materials design and the other is to optimize the output by installing the solar panels on a tracking base that follows the sun. This research employed the latter method. The main purpose of the thesis was to design and assemble of a dual-axis solar tracker with a view to assess the improvement in solar conversion efficiency. A comparative analysis was performed using three systems, i.e., Dual-Axis Tracking, Single-Axis Tracking and Stationary Modules. ¡®¡¯Design Expert 6.0¡± statistical software was used to process the design of experiment and to determine the effects of four chosen factors (Tracking or No Tracking, Type of Modules, Time of the Day, and Weather Condition). The results showed that the use of the Dual-Axis Tracking System produced 18% gain of power output, compared with a Single-Axis Tracking System. The gain of output power with the Dual-Axis Tracking System was much higher (53%) when compared with a stationary system inclined at 30¢ª to the horizontal. A benefit-cost analysis performed on the three systems showed that the unit cost of energy produced by the Dual-Axis Tracker is $0.53, which is reasonable, considering the state of the technology and the potential added benefit of any future amortization when employed on a large scale. Show less